In autoradiographic investigations designed to localize the sites of synthesis of complex lipids and proteins in peripheral nerve fibers, it was found (Gould and Dawson, 1976, Dawson and Gould, 1976, Gould, 1976), not unexpectedly, that incorporation of choline, fucose and lysine into phosphatidylcholine, glycoprotein and protein takes place in endoplasmic reticular-rich Schwann cell cytoplasm. Inositol incorporation into phosphpionsitides, in striking contrast, was found to occur to a large extent in axoplasm, a structure morphologically ill-equipped for such synthesis. In the proposed investigation, an examination in depth will be made of phospholipid metabolism in the axon. The autoradiographic method will be further exploited to examine what other precursors are incorporated into axonal lipids. This approach, at present confined to metabolism in peripheral nerve, will be modified to assess if similar lipid synthesis takes place in central nervous system axons. Concomitantly, biochemical studies will be initiated to separate sites of axonal lipid metabolism from sites of glial lipid metabolism. These sites will be tagged in peripheral nerve, spinal cord, and several other tissue preparations during short in vivo or in vitro labeling periods with appropriate radioactive precursors. Various fractionation methods will be tested to then separate the different labeled sites, e.g. 14C-choline labeled sites, from 3H-inositol labeled sites. These studies will be extended to tag other synthetic sites as results with other precursors are determined by quantitative autoradiography. The purified fractions will be prepared in larger scale and characterized for protein and lipid compositions and enzyme makeup, especially as it relates to phosphoinositide and polyphosphoinositide turnover.